4 CIRCULAR 2 7, U. S. DEPARTMENT OF AGRICULTURE 



clubs, but this is safe only when the clubs are located at a consider- 

 able distance. Another important ^precaution in this connection 

 is to fumigate thoroughly the trucks or carts in which the diseased 

 material is carried before using these same trucks or carts for trans- 

 porting the fresh manure for new beds. The same is true where 

 freight cars are used. 



Rigid sanitation and thorough fumigation may be practiced, but 

 if care is not taken to select soil for casing which is free from all 

 possibility of contamination, all of the work and expense, including 

 collecting and burning the diseased material, house fumigation, and 

 purchase of disease-free spawn, will be of no avail. 



The extremely infectious nature of the fungus, the rapidity with 

 which it grows, and the great vitality of the spores make the most 

 painstaking care indispensable in prevention and control. The 

 spores, as already pointed out, may be carried in the manure, in the 

 casing soil, on boots and shoes, on tools and implements, and by wind, 

 water, and insects. All diseased material must be removed, disin- 

 fected, and destroyed as soon as the disease appears in order to pre- 

 vent the reproduction and spread of the disease. Places where the 

 fungus appears, the houses, the ground about them, the composting 

 yard — wherever the disease might be carried — should be thoroughly 

 sprayed or otherwise treated with a 2y 2 per cent solution of lysol or 

 some other strong disinfectant (1 gallon of formalin to 45 gallons 

 of water may be used) . 



As soon as the beds stop bearing the used compost should be put 

 where the fungus which it contains can not return to the houses. 

 As the disease does not attack other crops, the spent compost may 

 be sold, but only to farmers who do not live near mushroom-growing 

 establishments. 



FU^IIGATIOX 



Fumigation with formaldehyde or sulphur or both has been found 

 to be the most satisfactory means of control for the bubbles disease. 

 Many successful growers simply burn sulphur in the house while it 

 is empty- Where sulphur is used as a combination fungicide and 

 insecticide, the proportion of 5 pounds to 1,000 cubic feet of air 

 space is used. Less will kill the fungi but will not control the insects. 



Some years ago the department worked out a successful method 

 of control by means of formaldehyde gas, which is described below. 



To prepare for fumigation, remove completely all old bedding 

 material from the house and dispose of the bedding as alread} 7 de- 

 scribed. Thoroughly spray the house with water and keep it warm 

 and closed for about a week or 10 days. Select a warm, moist day 

 for fumigation, as the gas is then more effective. To insure sufficient 

 humidity, spray again with water the day before the fumigation is 

 to be performed. Close and seal the house, making it as nearly air- 

 tight as possible by pasting paper over all cracks and filling up all 

 openings to prevent the escape of gas. If leakage is allowed the 

 fumigation may be ineffective. 



Caution. — It is theoretically possible for formaldehyde to form 

 explosive mixtures with the air: consequently, care should be exer- 

 cised in its use and all flames kept away from the houses while they 

 are being fumigated. 



